"Irrespective of any issues concerning my own personal conduct, the rights of my client, Mr Saif al-Islam, were irrevocably prejudiced during my visit," she said.

She said recent events had "completely underscored that it will be impossible for Mr Gaddafi to be tried in an independent and impartial manner in Libyan courts".

She added that Libyan officials had "deliberately misled the defence concerning whether the visit with Mr Gaddafi would be monitored", and also seized confidential documents.

Ms Taylor said she would submit a report later this week. ICC spokesman Fadi el-Abdallah said it had no comment to make on Ms Taylor's remarks, but said judges would consider the findings as they deliberate Libya's application to prosecute him.

Saif al-Islam, who was once expected to suceed his father, was arrested in November, three months after anti-government forces overran the capital, Tripoli.

ICC apology

Both the ICC and Libya want to put Saif al-Islam Gaddafi on trial for crimes under the former regime

Ms Taylor, an Australian, had been part of a team sent to prepare Saif al-Islam's defence when she was accused of passing Saif al-Islam coded documents, allegedly written by his former right-hand man.

She and her interpreter from Lebanon, Helen Assaf, were then formally detained by militia in Zintan on suspicion of endangering national security.

Their two other colleagues, Russian Alexander Khodakov and Spaniard Esteban Peralta Losilla, remained with them out of solidarity.

The announcement of their release was made during a visit to Libya last week by ICC president Sang-Hyun Song, who also offered an apology for any "difficulties" caused by the mission.

The ICC has also told Libya it will investigate the claims of wrongdoing.

Ms Taylor's team are also scheduled to appear before a court in Tripoli on 23 July for a final ruling on their case, a senior member of the Libyan attorney-general's office told the BBC.